Air lift pumps, employing a series of cylinders that are alternately filled and exhausted, are shown in my U.S. Pat. No. 3,730,983, but, although timers greatly assist in the effeciency of the pumping operation, in stripping fields where the easily produced fluid has been taken by conventional means, even with the use of timers, often more air than oil is pumped. It is an object of the invention to increase the effeciency of this type of production, so that the pump is activated only when the control cylinder is filled to the preselected degree with production fluid.